In microwave circuit design, it is often necessary to interface circuit boards with other circuit components such as microwave waveguides. Circuit boards typically communicate via one of various conductor-based transmission lines, such as microstrip, stripline, coplanar waveguide or slotline. Three-dimensional microwave waveguides typically have rectangular or circular cross sections, and are hollow with metallic shells or are filled with a conductive dielectric material. These three-dimensional waveguides are referred to herein as microwave waveguides or simply waveguides.
Adaptors or transitions, also referred to herein as probe launches or simply probes, are mechanisms employed to interface conductor-based transmission lines with waveguides. Such transitions typically suffer from losses due to attenuation and impedance mismatches (reflections), and also may result in perturbations in microwave signals sent or received by the probe.
Conventional transitions to a microwave waveguide are made from stripline or microstrip transmission lines. The transition may be disposed at an end of a microwave waveguide section, or laterally through a side of a microwave waveguide.